A Houston Chronicle article last week noted that a family of four in this city needs to make $63,600 a year simply to keep food on the table, a car running, a roof overhead ("What does it cost to live decently here?" Page A1, Thursday). Merely to get by, in other words. Houston is a relatively inexpensive place to live, particularly for a big city, but an income of $63,000 or less leaves little for eating out, taking vacations or saving for college.

Another Chronicle article ("Paydays especially joyous at the top," Page D1, Sunday) revealed that Houston's top-paid executive took home more than $57 million in 2012. (That, by the way, is about $156,000 a day.) Not bad work if you can get it - or, through hard work, good fortune and an eye for opportunity you can make it happen.

Huge compensation packages don't leave us breathless; we see them as signs of success. Since the Allen Brothers plied a murky, malarial bayou and imagined a great city on its banks, those who take risks, those with ideas and drive and daring usually have been rewarded.

At the same time, we remember the words of President John F. Kennedy: "To those whom much is given, much is expected."

The most fortunate among us traditionally have recognized that we are all Houstonians, whether we make $60,000 a year running a small business or less than a third of that cleaning offices late at night, and they have taken it upon themselves to reinvest in the city and its people. Whether it's Jesse Jones (this newspaper's second owner and founder of the Houston Endowment) or the Hoggs, the Worthams, the Rices, the Hermanns and others, Houston's legacy of civic philanthropy runs deep. These days such givers and visionaries as the Kinder Foundation and the Laura and John Arnold Foundation nurture that legacy.

A major challenge today for those who have the means is to invest in programs and opportunities designed to make sure that Houston is, indeed, a city of opportunity for all. The New York Times reported on Monday on a recent study that found that income mobility in Houston and other American cities, particularly in the South, is in danger of becoming sclerotic. Children born into the bottom fifth of income in our part of Texas have a less than 10 percent chance of making it into the top fifth in income. Born poor, they're likely to stay poor.

According to the Pew Research Center - quoted in an article in the current issue of Smithsonian magazine lauding Houston as "the next great American city" - "Houston is the most income-segregated of the 10 largest U.S. metropolitan areas, with the greatest percentage of rich people living among the rich and the third-greatest percentage of poor people among the poor."

That's ominous, Rice University sociologist Stephen L. Klineberg tells the Smithsonian writer. "The great danger for the future of America is not an ethnic divide but class divide," he warns. "And Houston is on the front line, where the gulf between rich and poor is widest. This is where America's future is going to be worked out."

We would suggest that those on last Sunday's list of the wealthiest among us help keep the class lines elastic, that they help to make sure that Houston offers opportunity for all, just as it has for them. Seek out a program like Genesys Works that finds meaningful internships for high school students. Get involved with schools such as Cristo Rey, a remarkable educational experience for low-income kids that builds real-life work into the curriculum. Help the Children's Defense Fund, a leading advocate for the disadvantaged in Texas.

Opportunities abound to continue building a vibrant, opportunity-rich city. Charitable contributions they may be, but they also are investments - investments that benefit us all.